Comparative transcriptome analysis quantifies immune cell transcript levels, metastatic progression and survival in osteosarcoma

Overall survival of patients with osteosarcoma (OS) has improved little in the past three decades and better models for study are needed. OS is common in large dog breeds and is genetically inducible in mice, making the disease ideal for comparative genomic analyses across species. Understanding the level of conservation of inter-tumor transcriptional variation across species and how it is associated with progression to metastasis will enable us to more efficiently develop effective strategies to manage OS and improve therapy. In this study, transcriptional profiles of OS tumors and cell lines derived from humans (n=49), mice (n=103) and dogs (n=34) were generated using RNA-sequencing. Conserved inter-tumor transcriptional variation was present in tumor sets from all three species and comprised gene clusters associated with cell cycle and mitosis and with the presence or absence of immune cells. Further, we developed a novel Gene Cluster Expression Summary Score (GCESS) to quantify inter-tumor transcriptional variation and demonstrated that these GCESS values associated with patient outcome. Human OS tumors with GCESS values suggesting decreased immune cell presence were associated with metastasis and poor survival. We validated these results in an independent human OS tumor cohort and in 15 different tumor data sets obtained from The Cancer Genome Atlas (TCGA). Our results suggest that quantification of immune cell absence and tumor cell proliferation may better inform therapeutic decisions and improve overall survival for OS patients.

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